In at least some internal combustion engines, a connecting rod is connected to a piston using a piston pin. When installed, the piston pin extends through a bushing on the connecting rod such that first and second ends of the piston protrude from opposite sides of the bushing. The first end of the piston is positioned within a first pin boss on a first side of the piston, and the second end of the piston is positioned within a second pin boss on a second side of the piston. Typically, the piston is coupled to the first and second pin bosses in one of three different configurations. In a first configuration, the piston pin is rotatably and axially fixed to the bosses. In this “fixed pin” configuration, the connecting rod is permitted to rotate about the piston pin, but the piston pin does not rotate within the bosses. In a second configuration, the piston pin is rotatably and axially fixed to the connecting rod. In this “semi-floating pin” configuration, the piston pin is permitted to rotate within the bosses; however, the connecting rod is fixed to the piston pin such that the piston pin and connecting rod rotate together. In a third configuration, the piston pin is axially, but not rotatably, fixed to the bosses using a pair of circlips (also known as a c-clip or snap ring). In this “full-floating pin” configuration, each circlip is positioned within a groove in a respective one of the bosses, and the piston pin is trapped between the pair of circlips. The piston pin is permitted to rotate within the bosses, and the connecting rod is permitted to rotate about the piston pin.
In a “full-floating pin” configuration, rotation of the piston pin against each circlip can cause the circlip to rotate. If one end of the circlip rotates closer to the other end, then the circlip can compress, possibly resulting in the circlip being inadvertently released from its groove. Further, rotation of the circlip can cause the circlip to wear, possibly resulting in failure of the circlip.
Great Britain (G.B.) patent number 359,836 discloses a circlip having curved serrations or scallops spaced at equal intervals around its circumference, where the serrations impart resilience to the circlip without interfering with the circlip's strength. When expanded into its operative position, the circlip prevents axial displacement of a grudgeon pin during operation. However, G.B. patent number 359,836 does not address limiting rotation of the circlip so as to limit wear or inadvertent release of the circlip.